Don't mean to dig up an old thread but, since this is the only one that seems to mention the MP5SD 9mm barrel specs, I think the specs specified by
@AviatorDave
may be (not saying that he is) incorrect or that I misunderstood.

The barrel of the SD 9mm past the ports on the German barrel has a OD (outer diameter) of about 0.560, not 0.867, as 0.867 would not clear the first few baffles in most MP5SD 9mm suppressors.

Don't mean to dig up an old thread but, since this is the only one that seems to mention the MP5SD 9mm barrel specs, I think the specs specified by
@AviatorDave
may be (not saying that he is) incorrect or that I misunderstood.

The barrel of the SD 9mm past the ports on the German barrel has a OD (outer diameter) of about 0.560, not 0.867, as 0.867 would not clear the first few baffles in most MP5SD 9mm suppressors.

Anyone can clarify this anomaly or did I overlook something?

If you look at post #5, he was asking only about the section of the barrel that contacts the trunnion, not the part of the barrel past the ports. I don't have an SD barrel, so I have no idea what they would be.